U.S. patent number 7,691,093 [Application Number 10/484,687] was granted by the patent office on 2010-04-06 for method of and apparatus for controlling flashback in an introducer needle and catheter assembly.
This patent grant is currently assigned to Becton, Dickinson and Company. Invention is credited to Greg L. Brimhall.
United States Patent |
7,691,093 |
Brimhall |
April 6, 2010 |
Method of and apparatus for controlling flashback in an introducer
needle and catheter assembly
Abstract
A method is provided for controlling the fluid flow rate in an
extension tube of an introducer needle assembly for use as
confirmation flashback. The introducer needle assembly has a
catheter attached to a catheter hub with a side port, an extension
tube attached to the side port on the catheter hub, and an
introducer needle with a notch adapted to be inserted into a bore
in the catheter. A lumber extends through the needle and is in
fluid communication with the notch. The needle has an outer
diameter smaller than the diameter of the bore such that an annular
space is defined between the catheter and the needle. The fluid,
typically blood, is at a pressure and has a viscosity when the
needle accesses it. A preferred minimum fluid velocity of the fluid
through the extension tube is selected (preferably at least 1 inch
per minute though the extension tube in certain applications). The
notch and the annular space are sized based, at least in part, on
the viscosity of the fluid and the pressure of the fluid to achieve
the preferred flow rate though the extension tube.
Inventors: |
Brimhall; Greg L. (West Jordan,
UT) |
Assignee: |
Becton, Dickinson and Company
(Franklin Lakes, NJ)
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Family
ID: |
30000545 |
Appl.
No.: |
10/484,687 |
Filed: |
June 20, 2003 |
PCT
Filed: |
June 20, 2003 |
PCT No.: |
PCT/US03/19667 |
371(c)(1),(2),(4) Date: |
January 23, 2004 |
PCT
Pub. No.: |
WO04/000407 |
PCT
Pub. Date: |
December 31, 2003 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050015071 A1 |
Jan 20, 2005 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60390349 |
Jun 21, 2002 |
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Current U.S.
Class: |
604/506 |
Current CPC
Class: |
A61M
25/0693 (20130101) |
Current International
Class: |
A61M
31/00 (20060101) |
Field of
Search: |
;604/165.03,168.01,165.02,256,260,164.02,164.06,166.01,167.06,207,246 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 750 916 |
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Jan 1997 |
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EP |
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0 747 083 |
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Apr 1997 |
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EP |
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0 747 085 |
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Apr 1997 |
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EP |
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2 343 118 |
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Sep 1999 |
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GB |
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WO 98/19725 |
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May 1998 |
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WO |
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WO 99/08742 |
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Feb 1999 |
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WO |
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Primary Examiner: Lucchesi; Nicholas D
Assistant Examiner: Koharski; Christopher D
Attorney, Agent or Firm: Ghose; Mony R. Metcalf; Craig
Kirton & McConkie
Parent Case Text
CROSS-REFERENCES TO RELATED APPLICATIONS
This application is a 371 of PCT US/03/19667 filed Jun. 20, 2003
which claims the benefit of provisional application 60/390,349
filed Jun. 21, 2002.
Claims
I claim:
1. A method of controlling the fluid flow rate in an extension tube
of an introducer needle assembly for confirmation flashback, the
introducer needle assembly having a catheter attached to a catheter
hub with a side port, an extension tube attached to the side port
on the catheter hub at least a portion of which is translucent, and
an introducer needle with a notch adapted to be inserted into a
bore in the catheter, wherein the needle has an outer diameter
smaller than the diameter of the bore such that an annular space is
defined between the catheter and the needle, the method including:
selecting a preferred fluid flow front rate of a fluid through the
extension tube, wherein the fluid is at a pressure and has a
viscosity when it is accessed by the needle; and selecting a needle
assembly from a plurality of needle assemblies capable of producing
the preferred fluid flow front rate, wherein each needle assembly
of the plurality of needle assemblies includes a distinct
combination of needle assembly properties, including the sizing of
the notch, the internal diameter of the extension tube, and the
annular space, and wherein each distinct combination provides a
distinct fluid flow rate through the extension tube based on the
pressure and viscosity of the fluid when accessed by the
needle.
2. The method of claim 1 wherein a porous material is located in
the extension tube at a location remote from the side port, further
including selecting the porosity of the material to achieve the
preferred flow rate.
3. The method of claim 1 wherein the preferred fluid flow front
rate is at least 1 inch per minute through the extension tube.
4. The method of claim 1 wherein the sizing of the notch is about
0.013 inch by 0.016 inch, the needle has an outer diameter of about
0.028 inch and the catheter has a bore with a diameter of 0.034
inch.
5. The method of claim 4 wherein the extension tube has an internal
diameter of 0.05 inch.
6. The method of claim 5 wherein the fluid is at a pressure of
about 30-50 mmHg and has a viscosity of 1.8 times that of
water.
7. The method of claim 6 wherein sizing the notch and the annular
space is based, at least in part, on the length of the
catheter.
8. The method of claim 6 wherein a porous material is located in
the extension tube at a location remote from the side port, further
including selecting the porosity of the material to achieve the
preferred flow rate.
9. The method of claim 1, wherein the introducer needle has a
length and the catheter has a length, and wherein the needle
assembly properties further includes the needle length and catheter
length.
10. A method of accessing a blood vessel comprising: selecting an
introducer needle assembly from a plurality of introducer needle
assemblies, the introducer needle assembly having a catheter
attached to a catheter hub with a side port, an extension tube
attached to the side port on the catheter hub at least a portion of
which is translucent, and an introducer needle with a notch adapted
to be inserted into the catheter such that the notch is disposed
within the catheter; inserting the tip of the introducer needle of
the selected introducer needle assembly into the blood vessel;
confirming insertion of the introducer needle in the blood vessel
by observing blood in the catheter near the notch; positioning the
tip of the catheter at a desired location within the blood vessel;
confirming positioning of the needle tip in the blood vessel by
observing blood flow through the extension tube; wherein the flow
rate of blood through the extension tube is based upon, at least in
part, a combination of the size of the notch, the size of the
internal diameter of the extension tube and the outer diameter of
the needle; wherein each introducer needle assembly of the
plurality of introducer needle assemblies includes a distinct
combination of the sizing of the notch, the internal diameter of
the extension tube, and the outer diameter of the needle, and
wherein each distinct combination provides a distinct fluid flow
rate through the extension tube, and wherein the selected
introducer needle assembly is selected to achieve a desired visual
flow front rate through the extension tube.
11. The method of claim 10 further including selecting the
introducer needle assembly based, at least in part, on the pressure
of the blood and the viscosity of the blood.
12. The method of claim 11 wherein the desired visual flow front
rate through the extension tube is at least 1 inch per minute.
13. A method of providing a needle assembly designed to control
flashback in an extension tube of the introducer needle assembly by
limiting fluid flow through the extension tube to a predetermined,
visual flow front rate, including: providing a translucent catheter
having a proximal end, a distal end and a central bore extending
from the proximal end to the distal end, wherein the bore has a
cross sectional area, wherein the translucent catheter is selected
from a plurality of catheters each having different cross sectional
areas; providing a catheter hub in fluid communication with the
central bore and having a proximal end and a distal end connected
to the proximal end of the catheter and a side port in fluid
communication with the catheter hub; providing an extension tube in
fluid communication with the side port at least a portion of which
is translucent, wherein the extension tube is selected from a
plurality of extension tubes each having a different internal
diameter; providing a seal affixed to the catheter hub and located
proximal of the side port, the seal sealing the proximal end of the
catheter hub; providing an introducer needle having a proximal end
and a distal end, and having a needle hub having a distal end and a
proximal end, the proximal end of the introducer needle connected
to the distal end of the needle hub, the introducer needle adapted
to be positioned within the catheter in an insertion position
wherein the distal end of the introducer needle extends distally
past the distal end of the catheter; the introducer needle having a
cross sectional area that is less than the cross sectional area of
the central bore such that an annular space is defined between the
introducer needle and the catheter; providing a notch at the distal
end of the introducer needle located within the catheter when the
introducer needle is in the insertion position such that fluid can
communicate between the notch at the distal end of the introducer
needle and the side port but is prevented from passing out of the
proximal end of the catheter hub by the seal; wherein the
introducer needle is selected from a plurality of introducer
needles each having a different combination of cross sectional
area, cross sectional area of the central bore, and notch size,
wherein the selected introducer needle, extension tube and
catheter, in combination, control the flow of fluid through the
extension tube such that a controlled visual flow front rate is
established through the extension tube.
14. The method of claim 13 wherein the notch has an area of about
0.0002 inches.sup.2, the annular space is about 0.0012
inches.sup.2, the extension tube has an internal diameter of 0.05
inches, the fluid is at 30-50 mmHg and has a viscosity of about 1.8
times that of water.
15. The method of claim 13, wherein the seal includes a gel.
Description
FIELD OF THE INVENTION
This invention relates to the field of catheter and introducer
needle assemblies. Specifically, the invention relates to a method
of and an apparatus for controlling flashback in an introducer
needle and catheter assembly.
BACKGROUND OF THE INVENTION
Catheters, particularly intravenous (IV) catheters, are used for
directing fluid into or withdrawing fluid from a patient. The most
common type of IV catheter is an over-the-needle IV catheter. As
its name implies, an over-the-needle IV catheter is mounted over an
introducer needle having a sharp distal tip. With the distal tip of
the introducer needle extending beyond the distal tip of the IV
catheter, the assembly is inserted through the patient's skin into
a vein. Once placement of the assembly in the vein is verified by
flashback of blood in the needle, the needle is withdrawn, leaving
the IV catheter in place. In certain circumstances, the caregiver
may move the needle within the vein, or may displace the catheter
with respect to the needle, to locate the catheter in a desired
position before fully withdrawing the needle. The proximal end of
the IV catheter typically has a hub that is designed to be
connectable to an IV fluid supply line after insertion of the IV
catheter in a patient. In other applications, an IV set (known as
an "extension set") is attached before insertion into the
patient.
Although typical IV catheter and introducer needle assemblies
generally perform their functions satisfactorily, they do have
certain drawbacks. For example, certain IV catheter and introducer
needle assemblies typically require a flashback chamber located on
the proximal end of the needle. This location is inconvenient for
the healthcare worker because, during insertion of the assembly
into a patient, the healthcare worker's attention is directed to
the distal tip of the needle. Thus, in order to determine if the
needle is properly placed in a vein, the healthcare worker has to
divert his attention away from the point of insertion of the IV
catheter and introducer needle assembly into the patient. Even in
devices that permit visual confirmation of flashback at a location
near the needle tip, there is no distinct confirmation that the
needle remains in the vein as it is positioned by the caregiver.
Typically, flashback chambers are immediately filled with blood
upon the initial access of the vein and cannot be used to confirm
that the catheter assembly has maintained (or achieved again)
access to the vein.
SUMMARY OF THE INVENTION
It is therefore an object of one aspect of this invention to
provide a method for controlling the flashback rate in an extension
tube.
It is an object of another aspect of the invention to provide a
method of making an introducer needle and catheter assembly that
includes a controlled, visible flashback rate in an extension tube.
Specifically, catheter assembly may be designed to achieve initial
flashback at the needle tip, as well as distinct confirmation
flashback at a controlled rate when the catheter is located within
the patient's vein.
It is an object of another aspect of the invention to provide an
introducer needle assembly that permits initial flashback at the
needle tip, as well as distinct confirmation flashback at a
controlled rate when the needle assembly is located within the
patient's vein.
It is an object of another aspect of this invention to provide a
method of inserting a catheter into a patient's vein that permits
initial flashback at the needle tip, as well as distinct
confirmation flashback at a controlled rate over a predetermined
period of time while the catheter is located within the patient's
vein.
In accord with one aspect of the invention, a method is provided
for controlling the fluid flow rate in an extension tube of an
introducer needle assembly for use as confirmation flashback. The
introducer needle assembly has a catheter attached to a catheter
hub with a side port. An extension tube is attached at one end to
the side port on the catheter hub. The other end of the extension
tube is plugged with a porous material that permits air to pass but
restricts liquid flow. An introducer needle with a notch is adapted
to be inserted into a bore in the catheter. A chamber extends
through the needle and is in fluid communication with the notch.
The needle has an outer diameter smaller than the diameter of the
catheter bore such that an annular space is defined between the
catheter and the needle. The liquid or fluid, typically blood, is
at a pressure and has a viscosity when the needle accesses it. A
fluid flow path is created from the patient's blood vessel, through
the needle tip and through center of the hollow needle, through the
notch in the needle to the annular space, along the annular space
to the catheter hub and out the side port, and into the extension
tube.
In use, the caregiver inserts the introducer needle and catheter
assembly into the patient's vein. During insertion of the assembly,
the notch is maintained within the catheter. An initial flashback
is visible near the tip of the translucent catheter (and thus near
the point of insertion) as blood flows through the notch and into
the annular space. As the blood continues to flow, it passes
through to the extension tube where the caregiver can observe the
flow of blood in the extension tube (confirmation flashback) at a
controlled rate (referred to herein as the "visual flow front
rate"), as discussed below.
During design of the introducer needle and catheter assembly, the
geometry and materials of the assembly are selected to achieve a
desired visual flow front rate through the extension tube.
Particularly, it is desirable to control the flow rate such that
confirmation flashback occurs for a relatively long period of time,
permitting the caregiver to know for a longer period of time that
the tip of the catheter is within and in fluid communication with
the vein, as well as to understand the nature of the blood vessel
accessed. In one implementation of the instant invention for use in
connection with an integrated catheter assembly (that is, a
catheter assembly including an extension tube attached to the
catheter hub before insertion) intended for vascular access, a
desired minimum fluid flow rate of the fluid visible through the
extension tube (that is, the visual flow front rate) is selected to
be around 1 inch per minute. The determination is then made as to
which component of the catheter assembly is to be employed as the
"throttle," that is, the controlling element in the catheter
assembly. The geometry (and materials, in certain circumstances)
can then be designed to achieve the desired visual flow front
rate.
In another implementation of the invention, the notch and the
annular space are sized so that the size of the central chamber
within the needle acts as the throttle. Specifically, both the
notch and the annular space are designed to have cross-sectional
areas greater than the cross sectional area of the chamber running
through the needle. Consequently, the needle chamber acts as the
throttle. In the case of a 20 gauge needle, the needle chamber has
a diameter of 0.016 inches and a cross sectional area of about
0.00020 in.sup.2 (that is, .pi.*0.008.sup.2=0.0002 in.sup.2). The
annular space and the notch are sized appropriately to have larger
cross sectional areas. A 20 gauge needle has an outer diameter of
0.028 inches. A catheter appropriate for such a needle would be an
18 gauge catheter which has a bore with a diameter of 0.034 inches.
Consequently, the annular space has a cross sectional area of about
0.0003 square inches. The notch is also sized to have a minimum
area greater than the needle's central chamber. In the case of a
notch formed by grinding out a straight-sided opening in the needle
wall (resulting in a rectangular notch) through to the center of
the needle, the notch has a width equal to the diameter of the
needle chamber (i.e., 0.016 inches). The notch length in the axial
direction is selected to be equal to or greater than the
cross-sectional area of the chamber divided by the diameter of the
chamber. Consequently, in this case, the length is preferably at
least 0.0125 inches (that is, 0.0002 inches.sup.2/0.016
inches=0.0125 inches).
In such an assembly, the extension tube may be selected to have an
internal diameter of 0.05 inches, resulting in a cross-sectional
area of about 0.002 in. When used for peripheral vascular access,
the fluid is at a pressure between 10 mmHg-250 mmHg is (typically
about 45 mmHg) and has a viscosity of about 1.8 times that of water
at normal body temperature of 98.6.degree. F. when the needle tip
accesses it. The visual flow front rate is then typically about 1
inch per minute through the extension tube. Different blood
pressure and blood viscosity will affect the visual flow front
rate.
In other implementations, it is desirable to size the annular space
between the needle and the catheter (based, at least in part, on
the viscosity of the fluid and the pressure of the fluid) to act as
a throttle, restricting (and thereby controlling) the flow through
the flow path and achieving the preferred flow rate through the
extension tube. Alternatively, the notch may be sized such that it
acts as the throttle. Further, the porosity of the plug in the
extension tube may be designed such that it permits air to flow out
of the tube at a rate which acts as a throttle by preventing the
blood from entering the tube any faster.
In accord with aspects of certain implementations of the instant
invention, an integrated introducer needle and catheter assembly is
provided including a controlled flow rate through the extension
tube. A flow path is created by the introducer needle assembly from
the vein to the extension tube. The flow path extends from the tip
of the needle, through the needle chamber, through the notch, into
and along the annular space between the needle and the catheter,
and then into the central chamber of the extension tube via a
catheter hub. The porous plug permits air in the extension tube to
pass out as the chamber fills with blood. The geometry and material
properties of the assembly are selected to achieve a desired visual
flow front rate in the extension tube which can be observed by a
caregiver but which does not restrict flow in a manner that would
interfere with the delivery of fluids by the assembly after
insertion. Currently, it is preferred that the flow rate be
selected such that the extension tube fills at a rate of at least 1
inch per minute, but other rates may be desirable depending on the
application. Further, it will be appreciated that various
modifications of the geometry and material properties may be
employed and still practice aspects of the invention.
In accord with another aspect of the invention, a method of
accessing a blood vessel is provided. An introducer needle assembly
has a catheter attached to a catheter hub with a side port, an
extension tube attached to the side port on the catheter hub, and
an introducer needle with a notch adapted to be inserted into the
catheter. The tip of the introducer needle is inserted into the
blood vessel thereby positioning the tip of the catheter in the
blood vessel as well. Insertion of the introducer needle in the
blood vessel is confirmed by observing blood in the catheter near
the notch. The positioning of the needle tip in the blood vessel is
further confirmed by observing blood flow through the extension
tube. The visual fluid flow front rate of blood through the
extension tube is a predetermined rate based upon, at least in
part, the size of the notch, the size of the internal bore of the
catheter and the outer diameter of the needle. Additionally or
alternatively, the flow rate is controlled based, at least in part,
on the pressure of the blood and the viscosity of the blood, and on
the internal cross section of the extension tube.
In accord with yet another aspect of the invention, a method is
provided for controlling flashback in an extension tube of an
introducer needle assembly. A translucent catheter is provided
having a proximal end, a distal end and a central bore extending
from the proximal end to the distal end. A catheter hub is in fluid
communication with the central bore and has a proximal end and a
distal end connected to the proximal end of the catheter and a side
port in fluid communication with the catheter hub. An extension
tube is in fluid communication with the side port. The proximal end
of an introducer needle extends from the distal end of a needle
hub. The introducer needle adapted to be positioned within the
catheter in an insertion position wherein the distal end of the
introducer needle extends distally past the distal end of the
catheter. A seal is affixed to the catheter hub and located
proximal of the side port, sealing the proximal end of the catheter
hub. The introducer needle has a cross sectional area that is less
than the cross sectional area of the central bore such that an
annular space is defined between the introducer needle and the
catheter. A notch at the distal end of the introducer needle is
located within the catheter when the introducer needle is in the
insertion position such that fluid can communicate between the
notch at the distal end of the introducer needle and the side port
but is prevented from passing out of the proximal end of the
catheter hub by the seal. The introducer needle, the notch and the
central bore are sized to control the flow of fluid through the
annular space, thereby controlling the flow of fluid through the
extension tube.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects and advantages will be apparent upon
consideration of the following drawings and detailed description.
The preferred embodiments of the present invention are illustrated
in the appended drawings in which like reference numbers refer to
like elements and in which:
FIG. 1 is a perspective view of the IV catheter and introducer
needle in accord with an aspect of the invention;
FIG. 2 is a cross-sectional view of the invention taken along line
2-2 in FIG. 1 showing the assembly prior to insertion into a
patient with the needle in the forward position;
FIG. 2A is a cut-away view of the assembly taken along line 2A-2A
of FIG. 2.
FIG. 3 is a cross-sectional view of the assembly of FIG. 1 with the
needle in a retracted position;
FIG. 4 is a cutaway side view of the distal tip of the needle and
catheter with the needle in the forward position, depicting blood
flow through the needle and catheter.
FIG. 5 is a cutaway side view of the distal tip of the needle and
catheter with the needle in the forward position, depicting blood
flow through the needle and catheter, and having an enlarged
annular space.
FIG. 6 is a cutaway side view of the distal tip of the needle and
catheter with the needle in the forward position, depicting blood
flow through the needle and catheter, and having a narrowed annular
space.
DETAILED DESCRIPTION OF THE INVENTION
The catheter and introducer needle assembly 10 in accord with one
implementation of this invention is shown in FIG. 1. As depicted,
the assembly is an integrated catheter. It will be appreciated that
aspects of the instant invention may be employed with other
catheter and introducer needle assemblies, such as those disclosed
in U.S. Pat. Nos. 4,326,519; 5,810,780; 5,935,110; 5,676,656; and
5,879,334, each incorporated herein by reference. In accord with
one implementation of the invention, the catheter and introducer
needle assembly includes catheter 20 affixed to catheter hub 21 and
needle 40 affixed to needle hub 41. The catheter includes a central
bore 120 having a cross sectional area and may be formed of
translucent material (including transparent materials). As used
herein, "translucent" materials shall be construed to include
transparent materials, as well as materials that permit light to
pass but not clearly enough to be deemed transparent.
The needle 40 has an outer diameter sized such that the cross
sectional area of the needle is less than the cross sectional area
of the central bore 120 of the catheter 20. Consequently, an
annular space 60 (see FIG. 2A) is defined between the catheter and
the needle. The needle also includes a central chamber 160
extending axially through the needle. As discussed below, the
chamber is in fluid communication with a notch 42 in the
needle.
As shown in FIG. 2 before withdrawal of the needle 40 from the
catheter assembly 10, the distal end of the catheter 20 seals about
the needle 40, preventing distal flow of blood out of the catheter.
Catheter hub 21 includes a side port 22 which has an extension tube
50 connected and in fluid communication with the catheter hub 21.
The extension tube has a central chamber 54 and is made of a
translucent material. Side port 22 is in fluid communication with
the annular space 60 in the catheter 20 so that fluid infused
through extension tube 50 will pass into the patient once catheter
20 is properly positioned in the patient (even if the needle is
still in position in the catheter). Conversely, blood exiting a
patient's vein through catheter 20 can travel through extension
tube 50, whether the needle is still in the assembly 10, or not.
Scale markings 55 may be provided to assist the caregiver
appreciate the rate of blood flow through the extension tube, as
discussed below.
The proximal end of extension tube 50 (that is, the end remote from
the catheter hub) typically includes a standard luer lock adaptor
51 to allow the connection of an IV fluid supply line to extension
tube 50. Such an IV fluid supply line can be connected to extension
tube 50 prior to insertion of assembly 10 into a patient. The
adaptor may include a plug 53 formed of a porous material, which
permits the flow of air but prevents the passage of liquids, such
as blood. As discussed below, the porosity of the material may be
selected to control the flow rate of blood in the extension tube.
In certain applications, the porosity of the material is selected
to permit passage of 0.03 cubic centimeters of air per minute.
The proximal end of catheter hub 21 is sealed with an elastomeric
plug 29 (see FIG. 2) to ensure that fluid does not leak out of the
proximal end of catheter hub 21 once the needle is withdrawn. Plug
29 may be filled with gel, such as silicone gel. This gel would
seal the hole left by needle 40 when it is removed from catheter
hub 21. In addition, this gel would fill the notch 42 when needle
40 passes through plug 29. This would prevent fluid from leaking
through the notch tube 50, including lower tube portion 26,
connected thereto located toward the distal portion of catheter hub
addition thereto, the plug 29 could be a septum having an axial
length greater than the distance between the distal end of the
opening at the tip of the needle and the proximal end of the notch,
as disclosed in U.S. Pat. No. 6,506,181, incorporated herein by
reference.
As the catheter and introducer needle assembly 10 is inserted into
a vein, blood passes through the opening in the chamber 160 of the
needle 40, through the distal notch 42 and into the annular space
60. When the catheter 20 is translucent or transparent, flashback
of blood in needle 40 is then observed by the caregiver as the
blood passes through the notch into the annular space, thereby
giving an initial indication that the needle tip has successfully
accessed the vein. This initial indication is at the distal end of
the catheter, near the point of insertion into the patient--thus
providing nearly immediate visual feedback without requiring the
caregiver to divert his attention from the point of insertion. The
caregiver may manipulate the needle tip (and thus the catheter)
into a final desired location. Blood continues to flow through the
annular space 60, to the needle hub 21, through the side port 22
and through the extension tube 50.
Once the caregiver has positioned the catheter assembly 10 as
desired, he can look at the extension tube 50 to confirm that the
catheter tip is positioned within a vein. If properly located,
flashback in the extension tube continues at the observable,
controlled rate. The gauge markings 55 help the caregiver
appreciate the rate of continued flow. Needle 40 can then be
withdrawn from catheter hub 21 (see FIG. 3), leaving catheter 20 in
place in the patient's vein. The observable confirmation flashback
in the extension tube continues whether the needle is in place or
not (at least until the extension tube 50 is filled with blood).
Thus, the caregiver receives confirmation of proper catheter
positioning even after the needle 40 is withdrawn.
In certain traditional devices, the only flashback is nearly
immediate and complete from the initial access of the vein.
Consequently, the flash chamber (which may be an annular space
about the needle in the catheter, an extension tube or a distinct
flash chamber) is filled with blood, preventing confirmation of
venal access if the needle is moved. This is especially true when
using needles having larger gauge sizes. In such cases, the
flashback flow front may only be visible for a fraction of a second
preventing a caregiver from receiving continued feedback (i.e.,
confirmation flashback) over an extended period of time. In accord
with the instant application, however, the flow rate of blood
through the catheter is controlled to permit continuous, active
confirmation during a relatively long period of time despite the
manipulation of the needle. Specifically, the size of the notch 42,
the annular space 60 and the internal diameter of the extension
tube 50 are selected to cause blood to fill the extension tube over
a predetermined time. For example, these components may be sized to
cause blood to fill the extension tube at a rate of at least 1 inch
per minute when the blood is at 45 mmHg and has a viscosity of
about 1.8 times that of water at 98.6 degrees F. The extension tube
preferably has a length of 4 inches. Consequently, it will take up
to 4 minutes until the extension tube is filled with blood (at a
minimum rate of 1'' per minute). This allows the clinician a
relatively long time to have confirmation flashback at a rate that
is discernable. Such continuous, long term flashback also provides
the caregiver information about the blood vessel accessed--such as
whether it is a vein or an artery, whether there is pulsitile flow,
the color of the blood, the pressure of the blood, and so on.
It is noted that the blood in the extension tube 50 may provide
various observable characteristics to the caregiver, such as the
visual flow front rate, the color of the blood, whether the visual
flow front through the extension tube is pulsing, and so on.
Consequently, a caregiver may be able to differentiate venous and
arterial access by blood color (and flow rate) and by pulsitile
flow. Indeed, characteristics of the blood vessel, such as blood
pressure, may be observed by the flow rate of blood through the
extension tube. Thus, aspects of the instant invention provide
useful information to the caregiver beyond continued confirmation
of venous access.
In accord with certain aspects of the invention, the geometry and
material properties of the introducer needle and catheter assembly
10 may be "tuned" to achieve a desired visual flow front rate in
the extension tube 50 based upon the gauge of the needle 40 to be
employed. It is desirable that the visual flow front rate through
the extension tube 50 be no less than 1 inch per minute. When it is
determined that the annular space 60 shall be used as the throttle,
the flow, or resistance to the flow of blood at a given pressure,
in the introducer needle and catheter assembly is determined in
part by three factors--the area of the annular space 60 between the
catheter inner diameter and needle outer diameter, length of
catheter 20, and viscosity of blood. The catheter 20 length is
generally specified as part of the therapy that is needed (e.g.,
longer catheters to reach deeper veins and arteries) so that length
must also be accommodated by adjusting the annular space 60 so that
the proper confirmation flashback rate can be achieved in the
extension tube. For example, a 20 gauge catheter, having a length
of 13/4'' may require the annular space be increased in size
(compared to that of a shorter catheter) to achieve the desired
visual flow front rate despite this length. This could be
accomplished by reducing the outer diameter of the needle 40, thus
increasing the area of the annular space 6 and the resulting
confirmation visual flow front in the extension tube 50.
It is noted that, due to flow characteristics of fluids, as
catheter 20 length increases, the area of the annular space must
increase to maintain the same flow rate. Annular area/volume flow
rate relationships can be established for different introducer
needle and catheter assemblies. For example, 1.75'' length
catheters require a larger annular area to achieve the same minimum
acceptable flow front rate in the extension tube 50 that would be
able to be achieved with the shorter catheter lengths and a smaller
annular area.
In the application of the invention discussed immediately above,
the notch 42 and the needle chamber 160 are sized to have cross
sectional areas greater than or equal to the cross sectional area
of the annular space 60. Consequently, neither the notch nor the
chamber act as a throttle and the volume rate of flow in the
extension set can be controlled by controlling the size of the
annular space (which, in turn, is defined by the outer diameter of
the needle and the inner diameter of the catheter).
It is noted that, while depicted as a single rectangular cutout,
the notch can be any shape, including circular, oval or the like.
Further, the notch may be formed as a plurality of fenestrations in
the needle wall.
Referring now to FIGS. 4-6, other implementations of the invention
provide that the visual flow front rate through the extension tube
50 can be controlled by modifying the geometry of the needle 40 and
catheter 20. Specifically, as seen in FIG. 4, when the notch is
employed as the throttle, the size of the notch 42 can be modified.
When the notch 42 is longer (resulting in a larger cross-sectional
area), the flow rate through the needle and catheter assembly 10
increases, thereby increasing the visual flow front rate through
the extension tube 50. As shown in phantom, when the notch 42 is
shortened, flow rate through the needle and catheter assembly
decreases, thereby decreasing the visual flow front rate through
the extension tube.
Referring to FIG. 5, when the annular space 6 is employed as the
throttle the annular space 60 can be increased (by using a needle
40 with a smaller outer diameter, a catheter 20 with a larger inner
diameter, or both), thereby increasing flow rate through the needle
and catheter assembly 10, and thus increasing the visual flow front
rate through the extension tube 50. Conversely, the size of the
annular space 60 can be decreased (see FIG. 6). As such, the flow
rate through the needle and catheter assembly is decreased, and so
too the visual flow front rate through the extension tube.
Thus, it is seen that an IV catheter and introducer needle assembly
is provided that allows the healthcare worker to determine if the
assembly is properly placed in a patient's vein without the need
for the healthcare worker to divert his attention away from the
insertion site and to confirm proper placement after positioning
using controlled flashback in the extension tube (including
confirmation after removal of the needle). Further, a method is
provided for controlling flashback in the extension tube of an
integrated catheter assembly. As such, the designer of such
integrated catheters can ensure appropriate flashback rates,
allowing the caregiver to observe continuous flashback over a
selected period of time, depending upon the particular application.
This control can be achieved by altering the size of the annular
space between the needle and the catheter, the size of the notch in
the needle, the size of the chamber extending through the needle,
the size of the extension tube leading to the catheter adapter, the
porosity of the filter plug in the extension tube, and any
combinations of these.
* * * * *